JP5271675B2 - Pre-plastic injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preplasticating injection molding apparatus which prevents the corrosion of metal due to pitting corrosion in the upper part of the front wall of the injection cylinder chamber, in cases involving high-speed injection molding of a resin material plasticized at a low viscosity and suck back. <P>SOLUTION: In the preplasticating injection molding apparatus, a resin material plasticized in a plasticization cylinder is fed to an injection cylinder chamber within an injection cylinder through a connection passage connecting the plasticization cylinder with the injection cylinder and injected from an injection hole of an injection nozzle with a plunger, while the plasticized resin material is caused to flow out into the injection hole through a by-pass passage opened at a position nearly symmetrical to the injection hole in the connection passage opened to the peripheral edge of the front wall of the injection cylinder chamber. An auxiliary by-pass passage communicating with the injection hole is opened at a position close to the part where the corrosion is to occur, or close to the opening of the connection passage, and nearly symmetrical in the connection passage. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pre-plastic injection device that communicates a plasticizing portion and an injection portion through a communication passage and injects from an injection nozzle, and more particularly to a pre-plastic injection device characterized by its nozzle flow path.

  As a typical injection apparatus for injecting molten resin in an injection cylinder by an injection plunger (hereinafter simply referred to as a plunger), there is a pre-plastic injection apparatus. The injection apparatus is schematically shown in FIG. 1 except for the resin flow path specific to the present invention described later.

  The injection device includes a plasticizing part 2, an injection part 3, and a junction 11 that communicates them. The plasticizing section 2 includes a plasticizing cylinder 20, a plasticizing screw 21 in the cylinder 20, a rotation drive device 23 that rotates the screw 21, and a check device 22 that slightly advances and retracts the screw 21. . The injection unit 3 includes an injection cylinder 30, a plunger 31 in the cylinder 30, and an injection drive device 60 that advances and retracts the plunger 31.

  An injection nozzle 41 is fixed to the injection cylinder 30 of the injection unit 3 via a nozzle adapter 140 at its front end. The front end of the plasticizing cylinder 20 is connected to the side surface of the nozzle adapter 140 via the junction 11. Therefore, the plasticizing part 2 and the injection part 3 are communicated by the junction 11 through the communication paths 12 and 42. Reference numeral 13 denotes a communication path bush provided to prevent the molten resin from leaking at the contact surface between the junction 11 and the nozzle adapter 140.

  A front wall 43 having a shape substantially equal to the tip end surface 31 a of the plunger 31 is formed on the end surface of the nozzle adapter 140 on the injection cylinder 30 side. An injection cylinder chamber 32 is formed in a space surrounded by the front wall 43, the injection cylinder hole 30a, and the distal end surface 31a of the plunger 31. The front wall 43 has an opening (42a) in the communication passage 42 at one of the peripheral edges thereof, and an injection hole 44 in the center of the front wall 43 extending to the tip of the injection nozzle 41 (44a). (Refer to FIG. 3 except for a bypass channel 145 described later).

  Reference numeral 24 denotes a hopper for supplying a resin material from the rear end side of the plasticizing cylinder 20. Although not shown, band heaters are provided on the outer periphery of the plasticizing cylinder 20, the junction 11, and the injection cylinder 30.

  In such an injection apparatus, the resin material supplied from the hopper 24 is plasticized by the shearing heat generated by the rotation of the plasticizing screw 21 and the heating by the band heater, and is extruded by the rotation of the screw 21 to be communicated with the communication path 12. 42 is sent to the injection cylinder chamber 32. At this time, the check device 22 allows the plasticizing screw 21 to retreat by back pressure acting on the molten resin to be sent out, and opens the communication passage 12 on the plasticizing cylinder 20 side. Further, the fed molten resin is measured by the plunger 31 retracted and the amount of retraction. Next, the plunger 31 moves forward, and the molten resin is injected from the injection nozzle 41 at the tip of the injection cylinder 30 into a cavity of a mold apparatus (not shown). At this time, the check device 22 advances the plasticizing screw 21 to prevent backflow that closes the communication passage 12. Usually, after the above-described measurement, a check is performed, and then a suck back for preventing dripping from the injection nozzle 41, that is, an operation of slightly retracting the plunger 31 is performed.

  In the injection unit 3 described above, there is a problem that the molten resin stays in a region on the opposite side (substantially symmetrical) of the opening 42a of the communication passage 42 with respect to the opening 44a of the injection hole 44 of the injection cylinder chamber 32. This is because the flow of the molten resin deteriorates in the opposite portion because the opening 42 a of the communication passage 42 is open to one side of the front wall 43 of the injection cylinder chamber 32.

  Therefore, the applicant of the present application described in Patent Document 1 is a pre-plastic injection device having a nozzle flow path as shown in FIG. 3, that is, the front wall 43 of the injection cylinder chamber 32 (in Patent Document 1, the nozzle side wall surface of the injection chamber) The bypass passage 145 that communicates with the injection hole 44 at a position that is substantially symmetric with respect to the injection hole 44 that opens at the center of the front wall 43 of the communication passage 42 that opens at the peripheral edge of the description. A pre-plastic injection device has been proposed in which an opening (145a) is formed in the sub-path), and the distal end surface 31a of the plunger 31 has a middle-high shape compared to its peripheral portion. As a result, a portion of the molten resin that tends to stay in the injection cylinder chamber 32 is caused to flow out from the opening 145a of the bypass flow path 145 provided in that portion to the injection hole 44, thereby preventing the stay. Therefore, in practice, the bypass flow path 145 is only a secondary flow path that prevents stagnation, and thus has a smaller cross-sectional area than the cross-sectional area of the injection hole 44.

Japanese Patent No. 2615334

  However, in the injection device disclosed in the above-mentioned patent document, when high-speed injection molding is performed with a resin material plasticized to low viscosity and further suck back is performed, the contact surface between the injection cylinder 30 and the nozzle adapter 140 is used. Thus, metal corrosion due to pitting may occur in the vicinity of both sides of the opening 42a of the communication passage 42. If the molding is repeated further, the corrosion progresses so that the molten resin enters the joint portion between the injection cylinder 30 and the nozzle adapter 140, and finally the molten resin flows from the contact surface during the injection. It sometimes leaked out. The place of occurrence is a corner portion 32 a on the front wall 43 side of the injection cylinder chamber 32, and regions Z 1 and Z 2 on both sides of the communication passage 42 opening 42 a of the front wall 43. Garage.

  The mechanism of this corrosion is assumed as follows. In particular, when sucking back using a low-viscosity molten resin, the inside of the injection cylinder chamber 32 becomes negative due to the sucking back, and the gas that dissolves in the molten resin is manifested as bubbles, although only a little. . The bubbles are crushed at a time during high-speed injection, so that a high pressure is generated in an impact, and the high pressure acts on the upper corner portion 32a. Therefore, the pressure acting on the corner portion 32a suddenly changes from a negative pressure to a high pressure at each injection and exhibits a large pressure amplitude, and as a result, corrosion particularly occurs at that portion. As described above, what is more prominent on the upper side coincides with the fact that bubbles are generated in the upper part thereof. On the other hand, when the high viscosity molten resin is used, the above-mentioned corrosion does not occur because the bubbles as described above are not generated.

  In particular, the reason why the corrosion occurs only in a part of the regions Z1 and Z2 of the corner portion 32a is that the pressure acting on the region excluding the regions Z1 and Z2 does not have the large pressure amplitude as described above. it is conceivable that. This is because, in the vicinity of the opening 42 a of the communication path 42, the molten resin remaining in the communication path 42 acts as a cushion to reduce the high pressure, while the residual resin is drawn into the injection cylinder chamber 32. This is because the pressure is also reduced. Further, even in the region on the opening 145a side of the bypass channel 145, the molten resin flows out to the injection hole 44 through the bypass channel 145, so that the high pressure as described above does not occur, but remains in the bypass channel 145. The molten resin is drawn into the injection cylinder chamber 32 and the negative pressure is reduced.

  Therefore, the present invention reduces the large pressure amplitude acting on the partial areas Z1 and Z2 of the front wall 43 of the injection cylinder chamber 32 each time of injection, and prevents the corrosion of the metal on the front wall 43. Propose. In addition, a pre-plastic injection device is proposed in which the molten resin is less likely to stay in the injection cylinder than before.

In order to achieve the above problem, a pre-plastic injection device according to an embodiment of the present invention is an injection cylinder in which a resin material plasticized in a plasticizing cylinder is communicated via a communication passage that connects the plasticizing cylinder and the injection cylinder. The resin material is injected from the injection hole of the injection nozzle by the plunger, and the communication passage opened at the peripheral edge of the front wall of the injection cylinder chamber is substantially symmetrical with respect to the injection hole. In the pre-plastic injection device that causes the resin material to flow out to the injection hole by the bypass flow path and the sub bypass flow path that are opened at positions, the opening of the bypass flow path and the opening of the sub bypass flow path are the openings of the injection holes Are arranged at equal intervals of about 120 degrees on the same circumference .

  In the pre-plastic injection device of the present invention, a sub-bypass passage communicating with the injection hole is opened in the vicinity of the portion where metal corrosion has occurred on the front wall of the injection cylinder chamber. Therefore, at the time of injection, the molten resin can flow out to the injection hole through the flow path, and the shocking high pressure generated in the portion can be released from the injection hole. Further, when sucking back, the negative pressure generated in the portion can be reduced by drawing the molten resin remaining in the flow path into the injection cylinder. Therefore, in the present invention, the large pressure amplitude acting on the portion at each injection is reduced, and the corrosion is prevented. In addition, in the present invention, the opening portion of the sub-bypass channel also contributes to preventing the molten resin from staying.

  In addition, in the pre-plastic injection device of the present invention, the above-described corrosion prevention, as well as the bypass flow passage opening and the sub bypass flow passage opening are equally arranged at intervals of approximately 120 degrees on the same circumference, so that normal injection and In the color change, the molten resin can be evenly discharged to the injection holes.

  The pre-plastic injection device of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic sectional view of a pre-plastic injection device of the present invention. FIG. 2 is an enlarged view of the main part of the nozzle adapter of the present invention. FIG. 2 (a) is a longitudinal sectional view thereof, FIG. 2 (b) is a view taken along the line BB of FIG. FIG. 4C shows a cross-sectional view taken along the line CC in FIG. The pre-plastic injection device of the present invention is substantially the same as the constituent members of the pre-plastic injection device described in the background art except for a flow path such as a sub-bypass flow path, which will be described below. Is omitted.

  In the pre-plastic injection device 1 of the present invention, a plunger 31 is built in the injection cylinder 30 of the injection unit 3, and a nozzle adapter 40 is fixed between the front end of the cylinder 30 and the injection nozzle 41. The injection cylinder chamber 32 is formed so as to be surrounded by these members. Reference numeral 50 denotes a bolt for fixing the nozzle adapter 40 to the injection cylinder 30, and 48 denotes a bolt insertion hole of the nozzle adapter 40.

  In the nozzle adapter 40, a front wall 43 of the injection cylinder chamber 32 is formed on the end surface on the injection cylinder 30 side. An injection hole 44 communicating with the injection nozzle 41 is opened (44a) at the center of the front wall 43. A communication passage 42 communicating with the plasticizing cylinder 20 is opened (42a) at the peripheral portion of the front wall 43, and the opening 42a of the communication passage 42 is substantially symmetrical with respect to the opening (44a) of the injection hole 44. A bypass channel 45 communicating with the injection hole 44 is opened (45a) at an appropriate position. Note that the bypass channel 45 of the present invention has a different sign because its cross-sectional area is different from that of the conventional bypass channel 145 (see FIG. 3), as will be described later.

  In addition to this, in the present invention, a sub-bypass passage communicating with the injection hole 44 in the vicinity of the portion (Z1 and Z2 in FIG. 3) that may cause corrosion of the metal, that is, in the vicinity of both sides of the opening 42a of the communication passage 42. 46 and 47 are opened (46a and 47a). More specifically, the openings 46a and 47a of the sub bypass flow paths are connected to each other so as to sandwich the opening 42a of the communication path 42 on the front wall 43 of the injection cylinder chamber 32 with respect to the opening 42a of the communication path 42. It is formed at a substantially symmetric position with respect to a straight line connecting the opening 42 a of the passage 42 and the opening 44 a of the injection hole 44. The sub-bypass channels 46 and 47 are formed so that their cross-sectional areas are substantially equal. Further, the sub-bypass channels 46 and 47 are formed so that the respective angles with respect to the injection hole 44 are substantially equal (both are angles R4 in the figure).

  In such an injection part 3, during injection, the molten resin is caused to flow out from the auxiliary bypass flow paths 46 and 47 communicating with the injection hole 44, and an impact generated in a part that may cause metal corrosion. In addition to letting a high pressure escape from the injection hole 44, during suck back, the molten resin remaining in the sub-bypass passages 46 and 47 is drawn into the injection cylinder chamber 32, and a negative pressure generated in that portion is generated. Can be reduced. Accordingly, the pressure amplitude acting on the portion at each injection is reduced, and as a result, the corrosion can be prevented. Furthermore, since the auxiliary bypass flow paths 46 and 47 are opened on the side where the communication path 42 is opened, the secondary bypass flow paths 46 and 47 also contribute to prevention of stagnation in a region opposite to the opening 45 a of the bypass flow path 45.

  The injection section 3 is more preferably formed with the bypass channel 45 and the sub-bypass channels 46 and 47 as follows. That is, the opening 45a of the bypass flow path and the openings 46a and 47a of the sub bypass flow path are the same circle in the front wall 43 of the injection cylinder chamber 32, centered on the opening 44a of the injection hole 44 at the center of the front wall 43. It is preferable to arrange them at equal intervals of about 120 degrees (= angle R1 = angle R2) on the circumference. The bypass channel 45 and the sub bypass channels 46 and 47 are preferably formed so that the angles with respect to the injection hole 44 are substantially equal (angle R3 = angle R4). Further, the cross-sectional areas of the bypass channel 45 and the sub-bypass channels 46 and 47 are formed to be substantially the same. The total area of the total cross-sectional areas of the bypass flow path 45 and the sub bypass flow paths 46 and 47 is substantially equal to the cross-sectional area of only one conventional bypass flow path 145 (see FIG. 3). However, if the hole diameters of the flow paths 45, 46 and 47 are too small and difficult to process, the hole diameters must be increased, so that the sum of their cross-sectional areas is the above-described conventional flow path 145. May exceed the cross-sectional area. Even in such a case, the sum of the cross-sectional areas of the flow paths 45, 46 and 47 is set not to exceed the cross-sectional area of the injection hole 44.

  In the injection section 3 configured in this manner, the molten resin can be more evenly discharged from the bypass flow path 45 and the sub bypass flow paths 46 and 47 to the injection holes 44, so that the normal injection and color change are possible. convenient.

It is sectional drawing which shows the outline of the pre-plastic injection apparatus of this invention. It is the figure which expanded the principal part of the nozzle adapter of this invention, Comprising: A figure (a) is the longitudinal cross-sectional view, A figure (b) is a BB arrow line view of a figure (a), A figure (c) is a figure ( It is CC sectional drawing of b). It is the figure which expanded the principal part of the conventional nozzle adapter, Comprising: A figure (a) is a longitudinal cross-sectional view, A figure (b) is a BB arrow line view of figure (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preplastic injection device 2 Plasticizing part 3 Injection part 20 Plasticizing cylinder 21 Plasticizing screw 30 Injection cylinder 31 Plunger 32 Injection cylinder chamber 40 Nozzle adapter 41 Injection nozzle 42 Communication path 42a Communication path of injection cylinder chamber front wall The opening 43 of the injection cylinder chamber 44 The injection hole 44a The opening 45 of the injection hole of the front wall of the injection cylinder chamber The bypass passage 45a of the present invention The openings 46 and 47 of the bypass flow path of the front wall of the injection cylinder chamber of the present invention Path 46a, 47a Sub-bypass passage opening 140 on front wall of injection cylinder chamber 140 Conventional nozzle adapter 145 Conventional bypass passage 145a Bypass passage opening R1 on front wall of conventional injection cylinder chamber R1 Angle R2 between the opening of the bypass flow path and the opening of the sub bypass flow path when centered in front of the injection cylinder chamber The angle between the opening between the sub-bypass passage when centered on the central portion

Claims (1)

The plasticized resin material in the plasticizing cylinder, the plasticizing cylinder and the injection cylinder through the communicating passage communicating were fed to an injection cylinder chamber within the injection cylinder, the injection of the injection nozzle the resin material by a plunger causes emitted from the hole, the communicating passage which is open to the periphery of the front wall of the injection cylinder chamber, the bypass passage and the secondary bypass flow path is opened at substantially symmetrical positions with respect to the injection hole, the resin material In the pre-plastic injection device that flows out into the injection hole,
The pre-plastic injection device , wherein the opening of the bypass flow path and the opening of the sub bypass flow path are equally arranged at an interval of about 120 degrees on the same circumference centering on the opening of the injection hole .

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